Curable epoxide composition

ABSTRACT

An object of the present invention is to provide a composite material including an epoxide resin, having an improved strength. The object can be solved by a curable epoxide composition comprising an epoxide compound; a carbon fiber; a curing agent; and phosphite ester or phosphate ester. According to the present invention, a strength of the curable epoxide composition comprising a carbon fiber can be improved.

TECHNICAL FIELD

The present invention relates to a curable epoxide composition.According to the present invention, a strength of the curable epoxidecomposition comprising a carbon fiber can be improved.

BACKGROUND ART

Carbon fiber has excellent properties such as high strength, highelastic modulus, and high conductivity, and is used in various compositematerials. As a matrix resin to be composited with the carbon fiber,there may be mentioned thermosetting resins and thermoplastic resins.For example, fiber reinforced plastic (FRP) can be obtained by addingfiber to thermosetting resin such as unsaturated polyester resin, vinylester resin, epoxy resin, or phenol resin.

Specifically, patent literature 1 exemplifies carbon fiber as a fiber tobe contained in a composite material comprising an epoxy resin.

CITATION LIST Patent Literature

[Patent literature 1] Japanese Translation Publication (Kohyo) No.2016-504476

[Patent literature 2] Japanese Translation Publication (Kohyo) No.2016-532000

[Patent literature 3] Japanese Unexamined Patent Publication (Kokai) No.3-177418

[Patent literature 4] Japanese Unexamined Patent Publication (Kokai) No.3-296525

SUMMARY OF INVENTION Technical Problem

On the other hand, patent literature 2 exemplifies carbon fiber as areinforcing fiber to be contained in a liquid curable epoxidecomposition. It is considered that the addition of carbon fiberincreases the strength of the composite material obtained from theepoxide composition. However, further improvement in strength isexpected.

Accordingly, an object of the present invention is to provide acomposite material including an epoxide resin, having an improvedstrength.

Solution to Problem

The present inventors found that by adding a phosphite ester or aphosphate ester to a liquid curable epoxide composition containingcarbon fiber, the physical properties of a cured product obtained bycuring are improved.

The present invention is based on the above findings.

Accordingly, the present invention relates to:

[1] a curable epoxide composition, comprising an epoxide compound; acarbon fiber; a curing agent; and phosphite ester or phosphate ester,[2] the curable epoxide composition of the item [1], wherein an averagefiber length of the carbon fiber is 20 μm to 1 mm,[3] the curable epoxide composition of the item [1] or [2], wherein anamount of phosphite ester or phosphate ester is 2 to 40% by weight,[4] the curable epoxide composition of any one of the items [1] to [3],further comprising a humed silica and/or a rheological agent[5] a coating material comprising the curable epoxide composition of anyone of the items [1] to [4],[6] an adhesive comprising the curable epoxide composition of any one ofthe items [1] to [4],[7] a molded body comprising the curable epoxide composition of any oneof the items [1] to [4].

Advantageous Effects of Invention

According to the liquid curable epoxide composition, the cured product(composite material) obtained from the liquid curable epoxidecomposition exhibits excellent flexural modulus or flexural strength.

DESCRIPTION OF EMBODIMENTS

The curable epoxide composition of the present invention comprises anepoxide compound; a carbon fiber; a curing agent; and phosphite ester orphosphate ester.

<<Epoxide Composition>>

The epoxide compound used in the present invention is not particularlylimited, but is preferably an epoxide compound used in the curableepoxide composition. Specifically, it is preferably an epoxide compoundhaving one or more epoxy group on average in the molecule thereof, andmore specifically it is an epoxy resin having more than one epoxy groupon average in the molecule thereof. The number of epoxy group is notparticularly limited so long as it is one or more on average, butpreferably two or more. The upper limit of the epoxy group is notparticularly limited, in view of an effect of epoxy resin on epoxy resincomposition. The term “average” means the average number of epoxy groupsin one molecule when two or more epoxy resins are mixed.

Specifically, the epoxide compound includes, for example, glycidylethers obtained by reacting epichlorohydrin with a polyhydric phenolsuch as bisphenol A, bisphenol F, bisphenol S, hexahydrobisphenol A,tetramethylbisphenol A, tetramethylbisphenol F, catechol, resorcinol,cresol novolak, tetrabromobisphenol A, trihydroxybiphenyl,bis-resorcinol, bisphenol hexafluoroacetone, hydroquinone, or bixylenol;polyglycidyl ethers obtained by reacting epichlorohydrin with analiphatic polyhydric alcohol such as glycerin, neopentyl glycol,ethylene glycol, propylene glycol, butylene glycol, hexylene glycol,polyethylene glycol, polypropylene glycol; glycidyl ether estersobtained by reacting epichlorohydrin with a hydroxycarboxylic acid suchas p-hydroxybenzoic acid, beta-hydroxynaphthalene carboxylic acid;polyglycidyl esters obtained from a polycarboxylic acid such asphthalic, methylphthalic, isophthalic, telephthalic, tetrahydrophthalic,hexahydrophthalic, endomethylenetetrahydrophthalic,endomethylenehexahydrophthalic, trimellitic or polymerized fatty acid;glycidylaminoglycidyl ethers obtained from aminophenol oraminoalkylphenol; glycidylaminoglycidyl ester obtained from aminobenzoicacid; glycidylamines obtained from aniline, toluidine, tribromoaniline,xylylenediamine, diaminocyclohexane, bisaminomethylcyclohexane,4,4′-diaminodiphenylmethane, 4,4′-diaminodiphenyl sulfone or the like;epoxypolyolefin; glycidylhydantoin; glycidylalkylhydantoin; triglycidylcyanulate; or mono-epoxide represented by butylglycidyl ether,phenylglycidyl ether, alkylphenylglycidyl ether, glycidyl ester ofbenzoic acid, stylene oxide or the like, and one or a mixture of two ormore thereof may be used.

An amount of the epoxide compound in the curable epoxide composition isnot particularly limited, but, for example, 25 to 95% by weight,preferably 30 to 90% by weight, most preferably 35 to 85% by weight. Thecurable epoxide composition can be efficiently cured, when the amount ofthe epoxide compound is within the above range.

<<Carbon Fiber>>

The carbon fiber use in the present invention is not particularlylimited, so long as it can increase the strength of the product (such asa composite material, molded body, adhesive, and coating material) whichis finally obtained. The carbon fibers include PAN-based carbon fibersmade from polyacrylonitrile resin, rayon-based carbon fibers made fromrayon, or pitch-based carbon fibers made from pitch.

An average fiber diameter of the carbon fiber is not particularlylimited, but generally 3 to 30 μm, preferably 4 to 20 μm, morepreferably 5 to 10 μm. Further, an average fiber length is notparticularly limited. In the present invention, for example, the carbonfiber having 20 μm to 10 mm may be used, but it is preferably 20 to 1000μm, more preferably 40 to 500 μm, even preferably 50 to 300 μm.

The average fiber length and average fiber diameter of the carbon fibermay be measured by using a general method used in this field. Inparticular, the carbon fibers are magnified by a magnifying glass or animage analyzer, and the fiber diameter or fiber length of about 10 to1000 of arbitrarily selected carbon fibers is measured. Then, bycalculating the average, the average fiber diameter and average fiberlength of the carbon fiber can be measured.

An amount of the carbon fiber is not particularly limited, but is, forexample, 1 to 40% by weight, preferably 10 to 35% by weight, mostpreferably 15 to 30% by weight. The strength of the coating material,adhesive, or molded body obtained by using the epoxide compound of thepresent invention can be increased, when the amount of the carbon fiberis within the above range.

<<Curing Agent>>

The curing agent contained in the curable epoxide composition of thepresent invention is not particularly limited, so long as they arecuring agents other than imidazole-based curing agent. There may bementioned modified polyamines such as an epoxy adduct, a Mannichreactant, a Michael reactant, a urea reactant, a thiourea reactant;polyamide polyamines; polythiols; dicyandiamide; dibasic dihydrazide;guanamines; acid anhydride; or melamine. Specifically, modifiedpolyamines, polyamide polyamines or polythiols are preferable, from theviewpoint of low-temperature curing. These curing agents can be preparedby known methods.

The epoxy modified polyamines include a compound obtained by mixing orreacting a compound in which N, N-dialkylaminoalkylamine is modifiedwith an epoxy compound, with a phenol resin and/or a polyhydric phenolcompound. The urea-modified polyamines include a compound in which N,N-dialkylaminoalkylamine is modified with urea (Patent literature 3), ora compound in which N, N-dialkylaminoalkylamine is modified withisocyanate (Patent literature 4). The thiourea-modified polyaminesinclude a compound in which N, N-dialkylaminoalkylamine is modified withthiourea, or a compound in which N, N-dialkylaminoalkylamine is modifiedwith isothiocyanate.

In the present invention, the curing agent(s) may be used alone or incombination of two or more.

An amount of the curing agent in the curable epoxide composition of thepresent invention is not particularly limited, and it may beappropriately determined according to the type of the curing agent. Theamount of the curing agent is, for example, 2 to 50% by weight, in oneembodiment, 5 to 30% by weight, and in one embodiment, 10 to 20% byweight.

The curable epoxide composition of the present invention furthercomprises a curing accelerator. The curing accelerator includes atertiary amine compound, a phosphine compound, an imidazole compound orthe like.

<<Phosphite Ester or Phosphate Ester>>

The curable epoxide composition of the present invention comprisesphosphite ester or phosphate ester.

As the phosphite ester, there may be mentioned phosphite monoester,phosphite diester, or phosphite triester. More specifically, there maybe mentioned monomethyl phosphite, dimethyl phosphite, trimethylphosphite, monoethyl phosphite, diethyl phosphite, triethyl phosphite,monobutyl phosphite, dibutyl phosphite, tributyl phosphite, monolaurylphosphite, dilauryl phosphite, trilauryl phosphite, monooleyl phosphite,dioleyl phosphite, trioleyl phosphite, monophenyl phosphite, diphenylphosphite, triphenyl phosphite, mononaphthyl phosphite, dinaphthylphosphite, trinaphthyl phosphite, di-o-tolyl phosphite, di-m-tolylphosphite, di-p-tolyl phosphite, di-p-chlorophenyl phosphite,di-p-bromophenyl phosphite, di-p-fluorophenyl phosphite, or the like,and one or a mixture of two or more thereof may be used.

As the phosphate ester, there may be mentioned monoester phosphate,diester phosphate, or triester phosphate. More specifically, there maybe mentioned monomethyl phosphate, dimethyl phosphate, trimethylphosphate, monoethyl phosphate, diethyl phosphate, triethyl phosphate,monobutyl phosphoric, dibutyl phosphate, tributyl phosphate, monolaurylphosphate, dilauryl phosphate, trilauryl phosphate, monooleyl phosphate,dioleyl phosphate, trioleyl phosphate, monophenyl phosphate, diphenylphosphate, triphenyl phosphate, mononaphthyl phosphate, dinaphthylphosphate, trinaphthyl phosphate, di-o-tolyl phosphate, di-m-tolylphosphate, di-p-tolyl phosphate, di-p-chlorophenyl phosphate,di-p-bromophenyl phosphate, di-p-fluorophenyl phosphate, or the like,and one or a mixture of two or more thereof may be used.

An amount of phosphite ester or phosphate ester in the curable epoxidecomposition is not particularly limited, but preferably 4 to 30% byweight, more preferably 5 to 25% by weight, most preferably 6 to 23% byweight.

The resulting cured product exhibits excellent flexural modulus orflexural strength, when the amount of phosphite ester or phosphate esteris within the above range

<<Silica>>

The curable epoxide composition of the present invention may comprisesilica.

A type of the silica is not particularly limited. There may be mentioneda humed silica, or a silica by wet method (such as a precipitated silicaor a silica gel), but preferably humed silica. By adding silica, amechanical property of the resulting cured product (composite material)can be improved, and a rheological property of the curable epoxidecomposition can be adjusted.

The humed silica is not particularly limited, so long as it is obtainedby a flame hydrolysis method (combustion hydrolysis method). The humedsilica can be prepared by flame-hydrolyzing silicon tetrachloride(SiCl₄) continuously.

(Hydrophilic Humed Silica)

The silica obtained by the flame hydrolysis method has a hydroxyl group(Si—OH) on the surface and is hydrophilic. The hydrophilic humed silicamay be used in the epoxide composition of the present invention.

(Hydrophobic Humed Silica)

The hydrophobic humed silica used in the present invention can beobtained, for example, by chemically treating the hydrophilic humedsilica obtained by the flame hydrolysis method (combustion hydrolysismethod), with silane or siloxane.

An average particle diameter of the humed silica is not particularlylimited, as long as the effect of the present invention can be achieved,but is 5 to 50 nm, preferably 7 to 40 nm, more preferably 10 to 25 nm.

Specifically, as the hydrophobic humed silica, there may be mentionedR972, R974, R104, R106, R202, R208, R805, R812, R812S, R816, R7200,R8200, R9200, R711, RY50, NY50, NY50L, RY200, RY200S, RX50, NAX50,RX200, RX300, R504, NX90S, NX90G, RX300, REA90, REA200, RY51, NA50Y,RA200HS, NA50H, NA130K, NA200Y, NX130, RY200L, R709, or R976S fromNippon Aerosil Co., Ltd.

An amount of the silica in the epoxide composition is not particularlylimited, but preferably 0.25 to 4% by weight. Further, the amount ofsilica is 0.3 to 4 parts by weight with respect to 100 parts by weightof total of epoxide compound and carbon fiber.

<<Rheological Agent>>

The curable epoxide composition of the present invention may comprise arheological agent. The rheological agent is not particularly limited aslong as the effect of the present invention can be achieved, but, forexample, there may be mentioned fatty amide, ethylenebisstearylamide,hexamethylenebishydroxystearylamide, modified urea, or urea modifiedpolyamide. The rheological agent of modified urea includes BYK-7410ET,BYK-410, BYK-410D, BYK-7411ES, BYK-411, BYK-7420ES, or BYK-420 (BYKChemie Japan K.K.).

(Other Additives)

Other components commonly used in this field can be added to the curableepoxide compound composition of the present invention, as long as theeffects of the present invention are not impaired. Specifically, forexample, there may be mentioned a polyimide resin, a polyester resin, apolyamide resin, or a resin such as a polyamideimide resin; a flameretardant, an antioxidant, an antifoaming agent, a leveling agent, orthe like.

<<Function>>

Although the mechanism by which the cured product obtained from thecurable epoxide composition of the present invention exhibits excellentflexural modulus or flexural strength has not been specificallydetermined but may be as follows. However, the present invention is notlimited by the following explanation.

The curable epoxide composition can increase the strength of theobtained composite material by containing the carbon fiber. The curableepoxide composition of the present invention comprises phosphate esteror phosphite ester.

It is considered that the phosphate ester or phosphite ester is presentat the interface between the carbon fiber and the matrix resin formedfrom the carbon fiber and epoxide. Then, it is presumed that phosphateester or phosphite ester improves the flexural modulus or flexuralstrength of the obtained cured product by improving the adhesion betweenthe carbon fiber and the matrix resin.

EXAMPLES

The present invention now will be further illustrated by, but is by nomeans limited to, the following Examples.

Example 1

Bisphenol A diglycidyl ether (80 parts by weight), a milled carbon fiber(20 parts by weight), and triphenyl phosphite (10 parts by weight) wereblended and mixed by stirring for 1 hour at room temperature using aplanetary mixer (PLM-2, INOUE MFG., INC), to thereby prepare an epoxycomposition in which milled carbon fibers were dispersed. Then, TXE-415A(16 parts by weight; polyaminoamide, T&K TOKA Co. Ltd.) was added to theresulting composition and the whole was mixed to thereby prepare acurable epoxide composition in which milled carbon fibers weredispersed. The viscosity, flexural modulus, and flexural strength of theresulting molded body were measured as follows.

<<Viscosity>>

The viscosity at 25° C. was measured using a cone-plate type viscometer.

<<Flexural Modulus and Flexural Strength>>

The obtained formulation was applied to a mold and was heated stepwiseat 60° C. for 1 hour and 150° C. for 1 hour, to thereby prepare a piecefor flexural test (80×10×4 mm) in accordance with JIS K7171. Theobtained test piece was subjected to a bending test (test speed: 2mm/min) using a universal tensile tester (Autograph AGS-X; ShimadzuCorporation).

Example 2

The procedure described in Example 1 was repeated except for furtheradding Aerosil R927 (0.5 parts by weight), to obtain a molded body.

Example 3

The procedure described in Example 2 was repeated except for furtheradding ethylenebisstearylamide (0.5 parts by weight), to obtain a moldedbody.

Example 4

The procedure described in Example 3 was repeated except thathexamethylenebishydroxystearylamide (0.25 parts by weight) is usedinstead of ethylenebisstearylamide (0.5 parts by weight), to obtain amolded body.

Example 5

The procedure described in Example 3 was repeated except that BYK7410ET(0.5 parts by weight) is used instead of ethylenebisstearylamide (0.5parts by weight), to obtain a molded body.

Example 6

The procedure described in Example 5 was repeated except that the amountof triphenyl phosphite was 15 parts by weight instead of 10 parts byweight, to obtain a molded body.

Example 7

The procedure described in Example 5 was repeated except that the amountof triphenyl phosphite was 20 parts by weight instead of 10 parts byweight, to obtain a molded body.

Example 8

The procedure described in Example 5 was repeated except that the amountof triphenyl phosphite was 30 parts by weight instead of 10 parts byweight, to obtain a molded body.

Example 9

The procedure described in Example 5 was repeated except that triphenylphosphate was used instead of triphenyl phosphite, to obtain a moldedbody.

Example 10

The procedure described in Example 5 was repeated except that tricresylphosphate was used instead of triphenyl phosphite, to obtain a moldedbody.

Comparative Example 1

The procedure described in Example 5 was repeated except that the amountof bisphenol A diglycidyl ether was 100 parts by weight instead of 80parts by weight, carbon fibers were not added, the amount of TXE-415Awas 20 parts by weight instead of 16 parts by weight, and triphenylphosphite was not added, to obtain a molded body.

Comparative Example 2

The procedure described in Example 5 was repeated except that triphenylphosphite was not added, to obtain a molded body.

Example 11

The procedure described in Example 5 was repeated except thatdicyandiamide (6.4 parts by weight) was used as the curing agent insteadof TXE-415A, and a curing accelerator (5.6 parts by weight;Fujicure1121; T&K TOKA Co. Ltd) was used, to obtain a molded body.

Example 12

The procedure described in Example 11 was repeated except that theamount of triphenyl phosphite was 15 parts by weight instead of 10 partsby weight, to obtain a molded body.

Example 13

The procedure described in Example 11 was repeated except that theamount of triphenyl phosphite was 20 parts by weight instead of 10 partsby weight, to obtain a molded body.

Example 14

The procedure described in Example 11 was repeated except that triphenylphosphate was used instead of triphenyl phosphite, to obtain a moldedbody.

Example 15

The procedure described in Example 11 was repeated except that tricresylphosphate was used instead of triphenyl phosphite, to obtain a moldedbody.

Comparative Example 3

The procedure described in Example 11 was repeated except that theamount of dicyandiamide was 8 parts by weight instead of 6.4 parts byweight, the amount of Fujicure was 7 parts by weight instead of 5.6parts by weight, the amount of bisphenol A diglycidyl ether was 100parts by weight instead of 80 parts by weight, carbon fibers were notadded, and triphenyl phosphite was not added, to obtain a molded body.

Comparative Example 4

The procedure described in Example 11 was repeated except that triphenylphosphite was not added, to obtain a molded body.

TABLE 1 Comp. Comp. Ex- Ex- Ex- Ex- Ex- Ex- Ex- Ex- Ex- Ex- Ex- Ex-ample ample ample ample ample ample ample ample ample ample ample ampleUnit 1 2 1 2 3 4 5 6 7 8 9 10 Bisphenol A diglycidyl ether g 100 80 8080 80 80 80 80 80 80 80 80 Milled carbon fiber¹⁾ g 0 20 20 20 20 20 2020 20 20 20 20 BYK7410ET²⁾ g 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5Ethylenebisstearylamide³⁾ 0.5 Hexamethylene- 0.25bishydroxystearylamide³⁾ Aerosil R927⁴⁾ g 0.5 0.5 0.5 0.5 0.5 0.5 0.50.5 0.5 0.5 0.5 TXE-415A⁵⁾ g 20 16 16 16 16 16 16 16 16 16 16 16Tripbenyl phosphite g 10 10 10 10 10 15 20 30 Triphenyl phosphate 10Tricresyl phosphate 10 Viscosity/25° C. Pa · s 22.7 39.3 10.9 10.8 11.813.2 17.8 12.6 10.3 6.0 22.5 20.6 Flexural modulus⁶⁾ GPa 2.4 6.1 7.0 6.98.0 8.2 8.9 9.0 8.9 7.5 7.8 8.1 Flexural strength⁶⁾ MPa 66 127 140 145160 164 165 174 164 109 138 142 ¹⁾PAN based, Fiber diameter 7 μm,Average film length 100 μm ²⁾Urea-modified liquid rheological agent³⁾Fatty amide (Thixotropic agent) Fatty amide manufactured by MitsubishiChemical (Nihon Kasei) Ethylenebisstearylamide (Slipacks E).Hexamethylenebishydroxysteariylamide (Slipacks ZHH) ⁴⁾Hydrophobic humedsilica (Average diameter of primary particle: about 16 nm) ⁵⁾Amide-basedcuring agent manufactured by T & K TOKA ⁶⁾Curing conditions: 60° C. × 1hr→ 150° C. × 1 hr

TABLE 2 Comp. Comp. Unit Example 3 Example 4 Example 11 Example 12Example 13 Example 14 Example 15 Bisphenol A diglycidyl ether g 100 8080 80 80 80 80 Milled carbon fiber¹⁾ g 20 20 20 20 20 20 BYK7410ET²⁾ g0.5 0.5 0.5 0.5 0.5 0.5 0.5 Aerosil R927⁴⁾ g 0.5 0.5 0.5 0.5 0.5 0.5 0.5Dicyandiamide g 8 6.4 6.4 6.4 6.4 6.4 6.4 Fujicure1121⁷⁾ g 7 5.6 5.6 5.65.6 5.6 5.6 Triphenyl phosphite g 10 15 20 Triphenyl phosphate 10Tricresyl phosphate 10 Viscosity/25° C. Pa · s 27.3 74.4 33.7 23.9 19.541.5 37.2 Flexural modulus⁶⁾ GPa 2.9 7.8 9.2 9.4 9.2 8.8 8.9 Flexuralstrength⁶⁾ MPa 89 149 169 175 172 160 164 ¹⁾PAN based, Fiber diameter 7μm, Average fiber length 100 μm ²⁾Urea-modified liquid rheological agent⁴⁾Hydrophobic humed silica (Average diameter of primary particle: about16 nm) ⁷⁾Imidazole-based curing agent manufactured by T & K TOKA⁶⁾Curing conditions: 60° C. × 1 hr → 150° C. × 1 hr

The viscosity was decreased by adding phosphite ester, or phosphateester, and thus the flexural modulus and flexural strength wereimproved.

INDUSTRIAL APPLICABILITY

The curable epoxide composition can be used in the coating material,adhesive, or molded body in which the physical properties are improved.

1. An adhesive comprising a curable epoxide composition, wherein thecurable epoxide composition comprises an epoxide compound; a carbonfiber; a curing agent; and phosphite ester or phosphate ester.
 2. Theadhesive according to claim 1, wherein an average fiber length of thecarbon fiber is 20 μm to 1 mm.
 3. The adhesive according to claim 1,wherein an amount of phosphite ester or phosphate ester is 2 to 40% byweight.
 4. The adhesive according to claim 1, the curable epoxidecomposition further comprises a humed silica and/or a rheological agent.5.-8. (canceled)